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Recently, auxetic honeycombs have attracted widespread attention with characteristics of lightweight, excellent energy absorption capacity and high shear stiffness. The present paper proposes the hybrid star-shaped tetra-chiral honeycomb (STCH) by embedding the tetra-chiral honeycomb (TCH) into the star-shaped honeycomb (SSH). The deformation mode and compression behavior of the STCH were studied numerically and compared with that of the SSH and TCH. Particularly, under the impact velocity of 2 m/s, the specific energy absorption (SEA) of the STCH increases by 80 and 179% than that of the SSH and TCH, respectively. Through investigating the effect of impact velocity and relative density on the crushing behavior of the STCH, the deformation modes map was summarized, and the empirical formula of the plateau stress was presented. Subsequently, the detailed parameter analysis of the STCH revealed that in a certain range, the SEA and stability of the STCH increase with the increase of N x , θ , and R , and with the decrease of L 2 and L 1. Finally, the improved STCH (ISTCH) with stable deformation and better crashworthiness was further proposed, and the crashworthiness of it was comprehensively compared with other structures. The result shows the excellent crashworthiness of the ISTCH. Particularly, the SEA of ISTCH can be nearly 8 times higher than that of the TCH. The novel star-shaped tetra-chiral honeycomb (STCH) can absorb more energy due to the increase of plastic hinges and the complex coupling deformation. The deformation modes map of the STCH was summarized and the plateau stress was fitted. The change of radius and cell wall angle can greatly change the Poisson's ratio from positive to negative. The STCH and improved STCH have excellent crashworthiness. [ABSTRACT FROM AUTHOR]

To enhance the out-of-plane mechanical performance, a novel honeycomb with arc-curved edge is proposed. The numerical model is built based on the elastoplastic failure criterion. The impact performance of proposed honeycomb is investigated and revealed. The influence of central angle and thickness on the crashworthiness is researched. The results show that the numerical result is in agreement with that of experimental test. The central angle has great influence on the deformation mode. The global buckling of edge tube is exhibited for the small central angle, and the consistent deformation mode is demonstrated for the central area. With the increasing of central angle, the energy absorption ability is enhanced for the plastic hinge could absorb more impact energy. The more stable deformation mode is exhibited for the larger central angle. The honeycomb with relatively large central angle has the best crashworthiness performance for the balance of energy absorption and structural mass. Compared with traditional honeycomb, the proposed honeycomb could improve the out-of-plane energy absorption characteristics. [ABSTRACT FROM AUTHOR]

Due to the high energy absorption capability and excellent bending strength of the sandwich panels, they are mostly preferred as protective structures against explosive blast attacks. The evaluation of their blast-mitigation characteristics through experiments is highly dangerous, costly, time-consuming, and polluting for the environment. Therefore, in this presented work, a series of numerical analyses were performed to evaluate the blast mitigation of the outstanding sandwich panels with honeycomb, corrugated, auxetic, and foam cores. The masses of sandwich panels were kept constant, and their areal densities were maintained constant throughout the study to effectively compare their performance under identical air blast loading conditions. To apply the air blast loads to the designed sandwiches, 1–3kg of spherical-shaped trinitrotoluene charges were used for a 100mm stand-off distance. The sandwiches are made of high-strength AL-6XN steel and crushable aluminum foam. The rate-dependent Johnson–Cook constitutive model of plasticity and the crushable foam model with volumetric hardening were used for the evaluation of sandwich panels’ plastic deformations. The findings of the work depicted that the honeycomb core is more efficient than the other core structures of the same masses because the sandwich panels with honeycomb core provide smaller back skin deflections, globalized core crushing, and higher core energy absorption than the other sandwich panels for extreme conditions of air blast loading. [ABSTRACT FROM AUTHOR]

This study extensively characterizes the out‐of‐plane stiffness and energy harvesting capabilities of a newly proposed anti‐trichiral hierarchical auxetic honeycomb structure, both mechanically and deformationally. By introducing a design concept based on the anti‐trichiral honeycomb (ATCH), a structure with superior out‐of‐plane load‐carrying capacity and excellent auxeticity is achieved. To validate the finite element model, compression simulations are conducted. Comparative investigations into the morphing characteristics and energy harvesting performance between the novel structure and the ATCH are performed. Additionally, the influence of various parameters on the comprehensive performance of the novel auxetic structure is explored. It has been found that the angle φ is most sensitive to the auxetic properties, while the ratio k significantly impacts energy absorption. This research advances the design of novel auxetic structures for potential applications in protective engineering. [ABSTRACT FROM AUTHOR]

AbstractTo enhance the performance of the six-missing rib honeycomb (ASRH), two axisymmetric missing rib honeycombs, ASRH-1 and ASRH-2, are proposed in this study. First, the in-plane impact performance of ASRH, ASRH-1, and ASRH-2 is experimentally compared to verify the accuracy of the finite element model. Then, the deformation patterns, specific energy absorption (SEA), and negative Poisson’s ratio (NPR) effects of the three honeycombs under different parameters were parametrically investigated. The results indicate that ASRH-1 and ASRH-2 exhibit higher SEA than ASRH at an impact velocity of 10 m/s, but the NPR effect does not change significantly. The axisymmetric honeycomb demonstrates no advantage at 50 and 100 m/s high-speed impacts. The Poisson’s ratio effect of the three honeycombs varied greatly with the internal ligament r of the honeycomb. The axisymmetric design offers a new concept for a NPR honeycomb design. [ABSTRACT FROM AUTHOR]

Honeycomb (HC) has been used in energy absorption applications due to its high stiffness and low density. Metallic HC are used for energy absorption applications, however, these metallic structures can be challenging to manufacture if complex geometric features designed to improve energy absorption are used, which motivates the use of additive manufacturing (AM). Metal AM methods include powder bed fusion (PBF) and direct energy deposition (DED). In addition to capital equipment cost, these processes possess challenges that include a required inert environment, powder handling, final part porosity, residual stresses, and nonuniform surface finish. These concerns can be alleviated through the use of polymer AM, however, polymeric parts exhibit brittle failure and have a lower stiffness than metallic HC structures. In this study, a low-cost 3D polymer printing method, stereolithography (SLA), is combined with a conventional electroplating process to fabricate a metal-plastic composite HC structure with energy absorption capability much greater than of a plastic HC structures of the same nominal volume. SLA parts have a smooth surface, so that the surface finish is at least as uniform after electroplating as the SLA part. The energy absorption characteristics of the electroplated HC is studied to determine how these energy absorbing materials can be manufactured at reduced cost. Our study confirms that the metal-plastic composite HC increases both the crush strain range and the mean crush stress of these samples, resulting in metal-plastic composite HC structures with substantially increased energy absorption. This study also examines how buckling initiators (BIs), or diamond shaped holes located at 50, 75, and 100% of the height of the hexagonal cell vertices, can influence energy absorption performance. This study shows that it is feasible to fabricate electroplated HCs, using an SLA preform, to achieve a substantial increase in energy absorption over using SLA alone. [ABSTRACT FROM AUTHOR]

Honeycomb structures have attracted wide attention due to outstanding mechanical properties as promising light material structures. Inspired by nature and artistic design, various honeycombs with different microstructural configurations have been designed for the sake of better mechanical performances and functions. Here, the Miura-origami reentrant honeycomb (MRH) structure integrating reentrant honeycombs (RH) and Miura-origami structures is investigated systematically. Dynamic impact behaviors of the present MRH structure are investigated numerically. The deformation modes and energy absorption capacity of RH and MRH are compared under different impact velocities, including low-velocity, medium-velocity and high-velocity. The results show that the plateau stress and the specific energy absorption(SEA) of MRH is much higher than RH. Moreover, the parametric study indicates that raising the inclined angle will decrease the plateau stress and the absolute value of Poisson'ratio for MRH structures. The specific energy absorption curves increase as the inclined angle of MRH grows up. In addition, the MRH with smaller dihedral angle can absorb much more impact energy and the variation of absorbed energy is proportional to the cell wall thickness of the MRH structure. This work is expected to provide a new thought for designing advanced energy absorption metastructures and achieving superior mechanical performances. [ABSTRACT FROM AUTHOR]

As a promising energy absorbing structure, reentrant honeycomb (RH) structures have been focus of interest in recent years. By reasonably adjusting the geometric configuration of the honeycomb cell, advanced structures with unique mechanical properties and deformation behaviors can be designed flexibly and novely. In this work, inspired by the composite laminates, a novel laminated reentrant honeycomb (LRH) structure is developed by controlling the orientations of RH layers for achieving excellent energy absorption capacity. Mechanical and deformation characteristics of the proposed structures under static and dynamic loadings are investigated experimentally and numerically. By comparing with single-layer RH structure with the same thickness, the results demonstrate that LRH structures have better energy absorption capacity. The deformation modes of RH and LRH structures are also discussed and it is noted that the LRH structure with ±30° honeycomb sublayers shows zero Poisson's ratio effect. It is worth emphasizing that LRH with 0° and 90° sublayers presents similar negative Poisson's ratio effect with RH by analyzing the equivalent Poisson's ratio-strain curves. In addition, it is found that the latter structure has the best energy absorption capacity when the thickness of single-layer 0° RH structure equals to 5 mm. This work provides a new and reliable thought to design the advanced protective structures under compression and impact loadings. [ABSTRACT FROM AUTHOR]

Based on a novel multi-arc concave cell, four types of thickness gradient honeycomb structures with positive gradient, negative gradient, symmetric positive gradient, and symmetric negative gradient are constructed by changing cell wall thickness, and the relative density of the structure is deduced. The in-plane impact dynamics of gradient structure are revealed by numerical method. The deformation collapse mode, the dynamic response curve, the energy absorption effect, and the platform stress of different gradient arrangement and impact velocity are analyzed. It is found that gradient arrangement and impact velocity have significant effects on the impact properties of the thickness gradient honeycomb structures. When the impact velocity is low, the structure shows laminar shrinkage deformation, but this phenomenon will gradually disappear with the increase of impact velocity. The results show that the energy absorption capacity of the negative gradient structure is the best under different impact velocities. The platform stress is greatly affected by the impact velocity and less affected by the gradient arrangement. [ABSTRACT FROM AUTHOR]

The application of bionic structures for the design of energy-absorbing structures has been proposed recently. The rapid advancement of additive manufacturing technology provides technical support for the fabrication of non-traditional structures and further improves the energy-absorbing properties of bionic structures. This work proposes a novel bionic hybrid structure that consists of honeycomb-inspired thin-walled tubes filled with weevil-inspired diamond TPMS (triple periodic minimal surface) structures. The energy-absorbing properties and the deformation behaviors of these topologies under axial crushing loads were investigated using combined numerical simulations and experimental tests. First, the effect of filling quantity and filling distribution on energy absorption of the hybrid structures was investigated. Results show that honeycomb tubes and diamond TPMS structures produce a synergistic effect during compression, and the hybrid structures exhibit excellent stability and energy absorption capacity. The bionic hybrid structure improves specific energy absorption (SEA) by 299% compared to honeycomb tubes. Peak crush force (PCF) and SEA are more influenced by filling quantity than by filling distribution. The effects of diamond TPMS structure volume fraction and honeycomb tube wall thickness on the energetic absorptive capacity of the hybrid structure were furthermore investigated numerically. Finally, a multi-objective optimization method was used to optimize the design of the bionic hybrid structure and balance the relationship between crashworthiness and cost to obtain a bionic hybrid energy-absorbing structure with superior performance. This study provides valuable guidelines for designing and fabricating lightweight and efficient energy-absorbing structures with significant potential for engineering applications. [ABSTRACT FROM AUTHOR]

Auxetic honeycomb sandwich structures (AHS) composed of a single material generally exhibit comparatively lower energy absorption (EA) and platform stress, as compared to traditional non-auxetic sandwich structures (TNS). To address this limitation, the present study examines the use of aluminum foam (AF) as a filling material in the re-entrant honeycomb sandwich structure (RS). Filling the AHS with AF greatly enhances both the EA and platform stress in comparison to filling the TNS with AF, while the auxetic composite honeycomb sandwich structure effectively addresses interface delamination observed in traditional non-auxetic composite sandwich structures. Subsequently, the positive–negative Poisson's ratio coupling designs are proposed to strengthen the mechanical features of a single honeycomb sandwich structure. The analysis results show that the coupling structure optimizes the mechanical properties by leveraging the high bearing capacity of the hexagonal honeycomb and the great interaction between the re-entrant honeycomb and the filling material. In contrast with traditional non-auxetic sandwich structures, the proposed auxetic composite honeycomb sandwich structures demonstrate superior EA and platform stress performance, suggesting their immense potential for utilization in protective engineering. [ABSTRACT FROM AUTHOR]

A modified 3D re-entrant honeycomb is designed and fabricated utilizing Laser Cladding Deposition (LCD) technology, the mechanical properties of which are systematically investigated by experimental and finite element (FE) methods. Firstly, the influences of honeycomb angle on localized deformation and the response of force are studied by an experiment. Experimental results reveal that the honeycomb angles have a significant effect on deformation and force. Secondly, a series of numerical studies are conducted to analyze stress characteristics and energy absorption under different angles (α) and velocities (v). It is evident that two variables play an important role in stress and energy. Thirdly, response surface methodology (RSM) and the Non-Dominated Sorting Genetic Algorithm II (NSGA-II) are implemented with high precision to solve multi-objective optimization. Finally, the final compromise solution is determined based on the fitness function, with an angle of 49.23° and an impact velocity of 16.40 m/s. Through simulation verification, the errors of energy absorption (EA) and peak crush stress (PCS) are 9.26% and 0.4%, respectively. The findings of this study offer valuable design guidance for selecting the optimal design parameters under the same mass conditions to effectively enhance the performance of the honeycomb. [ABSTRACT FROM AUTHOR]

Based on the proposed multi-arc curved edge concave adjustable Poisson's ratio cell, five kinds of sandwich panels with negative Poisson's ratio (NPR) were constructed by changing the in-plane thickness of cells: homogeneous, positive gradient, negative gradient, symmetrical positive gradient, and symmetrical negative gradient. The failure mechanical properties of the sandwich panels under the action of local impact were numerically studied. The influences of impact speed and gradient arrangement modes on the failure mode of the sandwich panels, the punch contact force (PCF) and the energy absorption effect (EAE) were investigated. It is found that the failure behavior of sandwich panels is different under different impact speeds. At the same impact speed, the thickness distribution pattern of the sandwich panel core layer will significantly affect the shock resistance of the panel. The study shows that the EAE of sandwich panels can be effectively enhanced by introducing gradient design method, and the sandwich panels with negative gradient arrangement show the best energy absorption effect. [ABSTRACT FROM AUTHOR]

The honeycomb sandwich panel presents a highly promising solution for enhancing ballistic behavior owing to its excellent strength-to-weight ratio and impact resistance. This study focuses on investigating the shock mitigation properties of honeycomb sandwich panels through experimentation and numerical simulation of high-velocity impact tests. Single-scale and double-scale hierarchical honeycomb cores are manufactured using selective laser melting with AlSi10Mg powder, combined with a pair of stainless steel (SS 316) sheets. High-velocity impact experiments were conducted within a velocity ranging from 100 to 270 m/s to examine the effects of different cores and projectile nose shapes on the dynamic response of the panels. Numerical simulations using ABAQUS/Explicit software were performed and validated against the experimental results. The sandwich panel with a double-scale hierarchical honeycomb core exhibited 7.8% and 6.1% more energy absorption compared to the single-scale hierarchical honeycomb core against conical and hemispherical nose projectiles, respectively. Additionally, the ballistic limit for the hemispherical projectile was found to be 8.9% higher than the conical-nose projectile under the same impact velocity and panel thickness. Moreover, an increase in panel thickness from 12 mm to 25 mm prompted a significant improvement of approximately 39% in specific energy absorption and a 44% increase in ballistic limit velocity. These findings highlight the considerable potential of single-scale and double-scale hierarchical honeycomb sandwich panels for the development of threat-resistant structures in critical dynamic loading applications. [ABSTRACT FROM AUTHOR]

This study explores the design and performance of axisymmetric hexachiral honeycombs, utilizing the hexachiral honeycomb framework and axisymmetric design method. Four axisymmetric hexachiral honeycombs with distinct arrangements were developed: left–right symmetry hexachiral honeycomb (LSHH), up–down symmetry hexachiral honeycomb (USHH), central symmetry hexachiral honeycomb (CSHH), and subunits symmetry hexachiral honeycomb (SSHH). The deformation patterns and compression behaviors of these honeycombs were comprehensively examined through experimental and numerical simulations, and comparisons were made with a non-symmetric hexachiral honeycomb (NHH). The results indicate that symmetrically designed honeycombs exhibit a larger mean plateau stress than the asymmetrically designed the NHH during low-velocity impacts. The study further discusses deformation patterns, specific energy absorption, and the negative Poisson's ratio effect across the five honeycombs under different parameters. Notably, symmetrically designed honeycombs demonstrate superior specific energy absorption, and the negative Poisson's ratio effect becomes evident at an impact velocity of 10 m/s. However, the advantages of axisymmetric honeycombs diminish at higher impact velocities of 50 m/s and 100 m/s. The Poisson's ratio effects of symmetric honeycombs weaken with an increase in the circular ligament r of the honeycomb. Additionally, the study identifies that platform stress and SEA increase for honeycombs with horizontal cell numbers greater than 6. [ABSTRACT FROM AUTHOR]

Due to their high load-bearing capacity and excellent energy dissipation properties, metal honeycomb lightweight sandwich panels are commonly utilized as highly efficient weight-saving components in the automotive, aerospace, and military industries. Especially the auxetic honeycomb sandwich panels have higher yield strength, more robust shear modulus, fracture toughness, less fatigue expansion, and higher vibration and energy absorption. In this paper, the ballistic resistance and energy absorption mechanisms of a novel re-entrant auxetic honeycomb (RSH) sandwich panel are investigated. The ballistic limits and energy absorption of the re-entrant star-shaped honeycomb (RSH), star-shaped honeycomb (SSH), and re-entrant star-shaped honeycomb (RH) sandwich panels are compared and analyzed, as well as the deformation mechanism during projectile penetration. The results show that the RSH sandwich panel has the best in-plane ballistic performance among the three types of honeycomb sandwich panels. For the same relative density, the ballistic limit of the RSH sandwich panel is 17.4% and 7.1% higher than that of the SSH and RH sandwich panels respectively. In addition, the effects of different design parameters on the ballistic resistance of RSH sandwich panels are investigated by changing the panel thickness, the relative density of the core layer, the cell angle and the cell size. It can be concluded that increasing the thickness of the face sheet is more effective in improving the ballistic limit (perforation energy) of the RSH with a thinner core layer. However, increasing the relative density of the core layer is more effective in enhancing the ballistic limit (perforation energy) for thicker core layers. Cell size has a significant effect on the ballistic resistance of RSH sandwich panels compared to cell angle, especially at impact velocities close to the ballistic limit. [ABSTRACT FROM AUTHOR]

A honeycomb structure is a sandwich structure widely used in fuselage, among which the hexagonal honeycomb core is the most widely used. The energy absorption characteristics and impedance ability of the structure are the main reasons that directly affect the energy absorption characteristics of the honeycomb sandwich structure. Therefore, it is necessary to study the out-of-plane mechanical properties of the composite honeycomb sandwich structure. Based on the numerical simulation results, the energy absorption characteristics of several composite honeycomb sandwich structures are verified by drop hammer impact experiments. The research shows that the transient energy absorption characteristics of the composite honeycomb sandwich structure are mainly related to the cell size of the honeycomb structure. The smaller the size of the front cell, the stronger the overall impact resistance; the strength of the composite honeycomb sandwich structure exceeds that of 7075 aluminum alloy-NOMEX and carbon fiber-NOMEX honeycomb sandwich structures. In this paper, the energy absorption characteristics of composite honeycomb sandwich structures under different impact energy are compared and studied. The displacement, force and energy curves of energy absorption characteristics related to time variables are analyzed. The difference in protective performance between the composite honeycomb sandwich structure and existing airframe structure is compared and studied. The optimal structural design parameters of composite honeycomb sandwich under low-speed impact of drop hammer are obtained. The maximum energy absorption per unit volume of the designed honeycomb sandwich structure is 171.7% and 229.8% higher than that of the NOMEX-AL and NOMEX-C structures. The 6.4 mm and 3 mm cell sizes show good characteristics in high-speed buffering and crashworthiness. The composite honeycomb sandwich airframe structure can improve the anti-damage performance of the UAV airframe structure, ensure the same thickness and lightweight conditions as the existing honeycomb sandwich airframe structure, and improve the single-core bearing mode of the existing airframe structure. [ABSTRACT FROM AUTHOR]

In order to improve the impact resistance of sandwich panels under low-velocity impact, the lotus leaf vein is selected as a biological prototype to design a bio-inspired honeycomb (BIH) sandwich panel. ABAQUS is used to establish and effectively verify the finite element (FE) model of the BIH sandwich panel. To systematically compare and study the mechanical properties of BIH and conventional hexagonal honeycomb sandwich panels under low-velocity impact, the maximum displacement of face-sheets, the deformation mode, the plastic energy consumption and the dynamic response curve of the impact end are presented. At the same time, the performance differences between them are revealed from the perspective of an energy absorption mechanism. Furthermore, the influence of the circumscribed circle diameter ratio of the BIH trunk to branch (γ), the thickness ratio of the trunk to branch (K) and the impact angle (θ) on impact resistance is studied. Finally, the BIH sandwich panel is further optimized by using the response surface method. It can be concluded that, compared to conventional hexagonal honeycomb sandwich panels, the addition of walls in the BIH sandwich panel reduces the maximum deformation of the rear face-sheet by 10.29% and increases plastic energy consumption by 8.02%. Properly adjusting the structural parameters can effectively enhance the impact resistance of the BIH sandwich panel. [ABSTRACT FROM AUTHOR]

Lattice structures nowadays have gained a peak in research. Inspired by the honeycomb structure and fishbone, this study investigated lattice structures that can provide auxetic behavior and store maximum energy absorption during deformation mode. From that, the study involved designing and producing different modified lattices based on the honeycomb's structure and the fishbone's perspective. The specimens were 3D printed within fused filament fabrication techniques within the additive manufacturing platform of Euromed University of Fes. The conception, production, mechanical testing, and simulation have been employed to get optimum data analysis of the mechanical properties of the designed structures. The results observed under quasi-dynamic compression did not show significant densification behavior; but, the auxetic behavior was seen in all structures, while some suddenly collapsed. The experimental and numerical analysis demonstrated similar deformation behavior and strong agreement in their respective results. Nevertheless, some discrepancies in mechanical values were observed, with a relative percentage error of approximately 1% for both methods. Consequently, owing to the enhanced energy absorption observed in the V2 and V3 structures, it is evident that these modifications hold promise for optimizing the performance of these metamaterials in various practical applications. [ABSTRACT FROM AUTHOR]

To improve the impact resistance of the honeycomb, a self-similar spider-web hierarchical structure is introduced by adding smaller hexagons to the centers of the primitive cells in the underlying hexagonal network and connecting the vertices of the smaller hexagons to the center points of the cell walls via straight beams. The hierarchical structure is introduced into the regular hexagonal honeycomb (RH) cells, and some novel hierarchical bio-honeycombs are proposed for the development of innovative hierarchical bio-honeycombs. Compression simulation was performed to validate the finite element model. Subsequently, a finite element model of the bio-honeycomb was developed to investigate its out-of-plane crashworthiness. The results show that the introduction of bionic cells and the RH cell walls produces significant interaction effects, with more severe plastic deformation at their intersections and the formation of more folded flaps in the cell walls. The effect of geometric parameters on the crashworthiness of the novel biomimetic bio-honeycomb structures is further discussed. It is shown that smaller bionic honeycomb pore sizes are beneficial for improving the efficiency of material utilization. [ABSTRACT FROM AUTHOR]

The shape memory alloy (SMA) can deform pseudo-plastically under external load, based on which a reusable impact energy absorption structure was designed. According to the classical SMA constitutive model, the finite element model for thin-wall structures was established, and the dynamic characteristics such as deformation modes and energy absorption of different forms of honeycomb structures under different impacting velocities, were analyzed, and the optimal energy absorption performance of the SMA structures was obtained. In addition, through comparison of the energy absorption performance of the SMA honeycomb with that of the aluminum honeycomb, the energy absorption of the SMA honeycomb with different structure configurations was different from that of the aluminum honeycomb under different-velocity impacts, with the optimal structure changes. The work provides a reference for the selection and design of the SMA honeycomb structures. [ABSTRACT FROM AUTHOR]

With the advent of additive manufacturing, lattice structures have been of increasing interest for engineering applications involving light‐weighting and energy absorption. Several studies have investigated mechanical properties of various lattices made up of mostly unreinforced polymers and lack numerical analysis for reinforced lattice structures. In this paper, mechanical response of short fiber reinforced lattice structures under compression is investigated through experiments and numerical simulations. Three different 2D lattices namely, square grid, honeycomb, and isogrid along with their rotated counterparts were fabricated using 15% wt carbon fiber‐acrylonitrile butadiene styrene and experimentally evaluated through uniaxial compression testing up to 30% strain. As simulations on fiber‐reinforced lattices under large compressive strains are rarely performed and published, finite element models accounting for fiber orientation induced anisotropic mechanical properties and geometrical imperfections were developed to predict the stress–strain characteristics up to 30% compressive strains. The stress–strain curves predicted from the numerical simulations matches well with the experimental responses for various lattice geometries. Various failure mechanisms such as thin strut buckling, contact within the lattice, and fracture of struts under large deformation were investigated. Analyzing energy absorption characteristics of these lattices revealed that the honeycomb structures in horizontal configuration exhibits superior energy absorption capability. [ABSTRACT FROM AUTHOR]

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Auxetic re-entrant honeycomb (AREH) structures, consisting of a single soft or tough material, have long faced the challenge of balancing stiffness and rebound resilience. To achieve this balance, dual-material printing technology is employed to enhance shock absorption by combining layers of soft and tough materials. Additionally, a novel structure called the curved re-entrant honeycomb (CREH) structure has been introduced to improve stiffness. The selected materials for processing the composite structures of AREH and CREH are the rigid thermoplastic polymer polylactic acid (PLA) and the soft rubber material thermoplastic polyurethane (TPU), created utilizing fused deposition modeling (FDM) 3D printing technology. The influence of the material system and structure type on stress distribution and mechanical response was subsequently investigated. The results revealed that the dual-material printed structures demonstrated later entry into the densification phase compared to the single-material printed structures. Moreover, the soft material in the interlayer offered exceptional protection, thereby ensuring the overall integrity of the structure. These findings effectively serve as a reference for the design of dual-material re-entrant honeycombs. [ABSTRACT FROM AUTHOR]

To enhance the load‐bearing capacity and energy absorption capacity of the honeycomb, three kinds of star‐rhombus honeycombs (SRHs) are proposed by adding rhombic parts to the traditional star‐shaped honeycomb (TSH). The quasi‐static crushing responses of SRHs, including deformation mechanism, crushing stress, specific energy absorption (SEA), and Poisson's ratio, are studied based on the finite‐element (FE) method. The introduction of rhombic parts increases the number of plastic hinges, resulting in significantly higher crushing stress and SEA of the SRHs than that of the TSH. Among the SRHs, SRH‐A has the largest energy absorption, and the SEA value of SRH‐A is 98.2% higher than TSH. Then, parametric studies including wall thickness, cell wall angle, and spacing length between the vertices of the star‐shaped part and the rhombic part are carried out. The wall thickness and cell wall angle have the greatest influence on the crushing response of SRHs. Crushing stress and Poisson's ratio of SRHs can be adjusted by changing the wall thickness of the rhombic part. The configurations and geometric parameters of the rhombic part determine the Poisson's ratio of SRHs. This study provides effective guidance for designing star‐shaped honeycombs with enhanced load‐bearing capacity and energy absorption capacity. [ABSTRACT FROM AUTHOR]

As an alternative to the conventional concave hexagonal honeycomb structure (CHHS), a negative Poisson's ratio honeycomb structure with power function curve (NHPC) was devised. The relationship between the power function exponent (PFE) and normalized power function coefficient (NPFC) of honeycomb structure and its equivalent Poisson's ratio (EPR) was explored to identify the range of variables required for the negative Poisson's ratio effect. To investigate the in-plane mechanical properties and energy absorption characteristics of NHPC, the deformation mode, dynamic response, and energy absorption characteristics under various impact velocities were studied by constructing an in-plane impact simulation model. The results showed that NHPC obviously exhibited a negative Poisson's ratio effect on medium and low impact velocities, and the deformation was primarily uniform. As the NPFC increased, the honeycomb structure was less prone to stress concentration, while the peak crushing force (PCF) and the specific energy absorption (SEA) declined and the plateau stress increased. A multi-objective optimization experiment was operated with low PCF and high SEA as the targets within the range of design variables in order to generate the optimal NHPC. According to the experimental findings, the improved NHPC showed a 25.48 % reduction in PCF and a 19.29 % increase in SEA. This paper provides theoretical recommendations for improving the energy absorption and structural optimization of the honeycomb structure. [ABSTRACT FROM AUTHOR]

By utilizing 3D printing technology, experimental three-point bending (TPB) tests, and finite element analysis, six honeycomb structures with a variety of overall Poisson's ratios (PR) are studied and compared in terms of bending properties and failure mechanisms. Four novel honeycombs that are designed by hybridizing hexagonal and re-entrant units outperform benchmark conventional honeycombs in terms of load-carrying capacity. Architected hybrid geometry honeycombs with zero PR show excellent specific energy absorption capability in comparison to benchmark honeycombs, absorbing approximately 136.9% and 475.1% more energy under TPB. 3D-printed honeycombs consisting of hexagonal units face layer separation damage mode under bending, while honeycombs with re-entrant cells in their lattice fail with joint shear due to the angle of their struts towards loadings. Designing honeycombs with a hybrid geometry lattice can enhance the load-carrying capacity, specific energy absorption, flexibility, and flexural modulus of the structure under bending. Due to their superior performance, the proposed architected hybrid geometry honeycombs with various Poisson's ratios own promising applications in automotive, protective, and construction industries. [ABSTRACT FROM AUTHOR]

Most natural materials have rotational and hierarchical properties, so they can show excellent mechanical properties such as shear resistance and impact resistance. In order to further improve the energy absorption characteristics of vibration absorbing structures, a new type of honeycomb structure with integral rotation and group rotation is designed and characterized. The effects of the geometrical parameters of rotation Angle on the impact deformation mode, stress response curve and energy absorption characteristics of the honeycomb structure are studied through numerical simulation and experimental design. The results show that the overall honeycomb performance of 15° is better than that of 0°, the specific energy absorption is the results show that the overall honeycomb performance of 15° is better than that of 0°, the specific energy absorption is increased by 6%, the bearing capacity is increased by 320 N, and the crushing force efficiency is increased by 2%. Compared with the whole cell and the group cell, the specific absorption energy increased by 35%, 73% and 71%. The results of this paper provide a new insight into the impact performance of monolithic and grouped rotating honeycomb structures, which is helpful for the results of this paper provide a new insight into the impact performance of monolithic and grouped rotating honeycomb structures, which is helpful for the optimization of crashworthiness structural design. [ABSTRACT FROM AUTHOR]

In order to balance the blast protective performance and lightweight property, sandwich panels with various geometries of core are being employed in the military armours and modern-day combat vehicles. Owing to the superior energy absorption capacity of auxetic-reentrant cellular structures, hybridizing auxetic cells with the regular hexagonal cells in the honeycomb core for the purpose of blast protection could be a promising method. Therefore, novel honeycomb cores with combined auxetic and hexagonal cells (AuxHex and Star-Reentrant) are designed for blast protection panel with an aim to enhance the blast performance by improving the energy absorption and minimizing the dynamic deflection of the back plate. Initially, the dynamic response of honeycomb sandwich panels with various regular geometrical cores is analysed and validated with the experimental results from the literature. Further, air blast analysis has been performed on AuxHex and Star-Reentrant honeycomb cored sandwich panel having same relative density as that of hexagonal honeycomb core under exactly same conditions. In addition to that, the study is extended for varying charges of TNT and at different stand-off distances. It has been revealed that the sandwich panel with AuxHex and Star-Reentrant core of same relative density as that of hexagonal honeycomb core absorbs 28% and 19.2% more amount of energy and experiences 17% and 8% less deflection, respectively, than those with regular hexagonal honeycomb core. [ABSTRACT FROM AUTHOR]

Cellular hexagonal (conventional) and re‐entrant (auxetic) honeycombs are applicable in automotive, construction, and protective engineering. Auxetic structures own excellent energy absorption and flexural behavior due to their special deformation under loading. This work explores the performance of additively manufactured polylactic acid (PLA)‐ and thermoplastic polyurethane (TPU)‐based hexagonal and re‐entrant honeycombs under flexural loading via experimental three‐point bending (TPB) tests and finite‐element analysis (FEA). 3D‐printed conventional and auxetic cellular structures are filled with polyurethane (PU) foam and their energy absorption capacity and flexural modulus are compared with hollow structures. The results reveal that TPU‐based structures' energy absorption capacity and flexural modulus improve significantly, whereas the PLA‐based structures' performance deteriorates when filled with PU foam. Moreover, re‐entrant honeycombs are better reinforced with foam in comparison to the hexagonal honeycombs, as the re‐entrant's unit cell is more spacious than the hexagonal unit cell. Finally, parametric studies are performed via FEA to investigate the influence of geometric parameters of structures and flexural loading setup on the performance of the honeycombs, showing that structures with thicker struts and higher cell angle can act stiffer under TPB. The outcomes of this research indicate the promising performance of foam‐filled TPU‐based auxetic structures. [ABSTRACT FROM AUTHOR]

Energy-absorbing materials have extensive applications in aerospace and automotive applications. Research has shown buckling initiators, or triggers, in energy-absorbing tubular structures increase the energy absorbed by encouraging the side panels to fold when loaded out of plane in compression conditions. Additively manufactured TPE honeycombs were designed in this study to include these buckling initiators, which introduced a slight decrease in initial weight, as well as initial stress concentrations, while improving crashworthiness characteristics. The samples with buckling initiators (1BI) showed an increase in crush efficiency when directly compared to their no buckling initiator (0BI) counterparts. The 1BI samples maintained an increased crush efficiency regardless of the strain rate used. The samples with 1BI were able to better equilibrate the peak stress with the plateau stress. These honeycomb samples were found to maintain their crush efficiency, even after multiple rounds of compression testing. The quasi-static 0BI samples experienced a 23.4% decrease in the peak stress after multiple rounds of compression testing, while the 1BI samples saw approximately a 23.0% decrease. The 1BI samples averaged a decrease in crush efficiency of 0.5%, while the 0BI samples saw a decrease in crush efficiency of 5%. As the strain rate increased, the crush efficiency for the 1BI samples showed an increase in performance, with a smaller degradation in crush efficiency over multiple uses. Visco-elastic honeycomb with buckling initiators has a higher energy absorption than samples with no buckling initiators when exposed to multiple impact cycles. [ABSTRACT FROM AUTHOR]

In this paper a honeycomb paperboard filled with foam particles is presented. The effect of parameters such as the cell size, the honeycomb paperboard thickness and the foam particles size on the interaction, energy absorption capacity, and the half wavelength are investigated theoretically and experimentally. The experiment results show that foam particles of honeycomb paperboard increase their initial crushing strength and energy absorption and the stress in the honeycomb paperboard filled with foam particles rises exponentially during the crushing stage. Furthermore, decrease in the densification strain; increase in number of folds; and decrease in half wavelength are other results of this research. And the smaller the foam particles, the greater the effect of foam particles filling. In the theoretical section, the interaction between the foam particles and the honeycomb paperboard cell wall are studied by regarding as point contact. Expressions are derived to predict the stress and half wavelength of honeycomb paperboard filled with foam '''''''''''''''''''particles in the crushing stage. A comparison between theoretical predictions and experimental results shows that the theoretical models can effectively predict this stress. It is expected that these studies can help to improve the application of honeycomb paperboard and provide a reference for further research on foam particle filling. [ABSTRACT FROM AUTHOR]

Human society's need to build low-weight, high-strength and durable structures has increased the demand for composite materials. In this case, composites are used where high mechanical strength, low weight, sound and thermal insulation properties are required. One of the most important issues now is designing materials and coatings aimed at reducing heat loss and resisting high temperatures. One way to address this problem is to develop a technique for preparing and applying composite materials that slow down their heating applied to a surface. In this study, carbon nanotubes (CNTs) reinforced composites were fabricated using silicone molding to be applied to honeycomb sandwich structures. To determine the effect of CNTs on the thermal behavior of the sandwich panels, different weight percentages of this material (0.025, 0.05. 0.075 wt.%) were added to the epoxy resin. The results showed that the thermal stability of the epoxy composites was directly related to the increase in the percentage of CNTs as the CNT content increased to 0.075 wt.%, and the thermal degradation temperature of the epoxy composites increased by 14 °C. In addition, the energy absorption increased by 4.6% with an increase in CNTs up to 0.075 wt.%. Density measurements showed that the density of the nanocomposite samples increased by adding CNTs to pure epoxy resin. The actual densities of the samples reinforced with 0.025, 0.05, and 0.075 wt.% CNTs are 0.925, 0.926, and 0.927 of the theoretical density, respectively. Since the CNT dispersion uniformity in the epoxy matrix can significantly affect the properties of the composites, in this study, a new method of dispersing CNTs in the epoxy resin matrix resulted in higher thermal conductivity while using lower amounts of CNTs compared to other studies. The storage modulus of the epoxy matrix composites reinforced with 0.05 wt.% in this study was 25.9% and 6.9% higher than that from the previous study reinforced with 0.1 wt.% and 0.25 wt.% CNTs, respectively. Furthermore, the tanδ and loss modulus of the composite reinforced with 0.05 wt.% CNTs in this study were 52% and 54.5% higher than that from the previous study with 0.1 wt.% CNTs, respectively. This study provided an optimal approach for designers and engineers who want to effectively design their composite honeycomb sandwich structure with better thermal properties. [ABSTRACT FROM AUTHOR]

The performance of a multi-layer honeycomb skeleton can be significantly enhanced through tandem connection, while the structure's properties can be tailored by altering the layer stacking method of the honeycomb skeleton. To investigate the impact of layer stacking methods on the mechanical properties of multilayer honeycomb skeletons, 3D printing technology was used to prepare double-layer honeycomb skeleton tandem structures with different dislocation modes in compression testing. A finite element simulation model was established to conduct quasi-static simulation research. Compared to that of a single-layer honeycomb skeleton, the energy absorption of the honeycomb skeleton tandem structure increased. The optimal bearing capacity of the honeycomb skeleton was achieved when the upper and lower layers were precisely aligned. Once dislocation occurred, both the value of average platform stress and energy absorption decreased. Then, the bearing capacity of the honeycomb skeleton tandem structures increased with an enlargement of the dislocation, reaching its maximum at the half-dislocation period. An increase in the partition thickness and stiffness led to a reduction in the dislocation-induced effects on the mechanical properties. The research results can provide theoretical and data support for the engineering application of honeycomb skeleton tandem structures. [ABSTRACT FROM AUTHOR]

This study proposes to investigate the crushing performance of auxetic honeycombs by combining liquid and solid phase materials in one structure. The multiphase structures were produced by injecting a liquid Gallium metal into the hierarchical voids of the proposed metamaterials and tested at different temperatures (22 and 35 0C), where the melting temperature of Gallium metal is 29.4 0C. The deformation mechanism, compressive strength, absorbed energy, and Poisson's ratio (PR) of the samples was compared at different strains and at different temperatures. Results show that multi-material samples with Gallium metal lead to a progressive deformation mechanism and stabilize the fracture mechanism; however, they only exhibit larger compressive strength in a few cases. In addition, the effects of the phase change of Gallium from solid to liquid when the temperature increase from 22 0C to 35 0C stand out in the percent change of mechanical response. Overall, the presented samples in this work can be recommended to manipulate the collapse mechanism with a multi-material approach of liquid and solid constituents. [ABSTRACT FROM AUTHOR]

The design and exploration of novel structures in engineering, where unique structures can produce significant improvements in performance, has always been an important multidisciplinary research area. Unlike traditional manufacturing, the unique manufacturing concept of additive manufacturing (AM) enables the construction of complex structures with ease. Therefore, the exploration of novel structures by means of additive manufacturing has become a hot point of research in this field, taking full use of the advantages of AM. In this paper, we design a ribbed honeycomb structure based on the bionic principle and construct and study it by selective laser melting (SLM). The hardness, relative density, and structure are characterized at different combinations of scanning speed and laser power, and the best structure and properties are found at 1200 mm/s and 400 W. On the basis of these printing parameters, several groups of specimens with different structures were constructed again to investigate the deformation process and mechanical properties during the out-of-plane compression. It was found that the platform stress of the honeycomb could be increased by up to 19.0% after the addition of ribs, and the honeycomb with 10° rib inclination showed a rib-dominated deformation mode during the deformation process, in which the compression curve showed extremely regular and periodic fluctuations with a large range. [ABSTRACT FROM AUTHOR]

Structural hierarchy has become a popular technique to improve the crashworthiness of engineering structures. A study is conducted to explore the interaction between hierarchical geometries and determine the optimum honeycomb configuration that improves crashworthiness. Nine distinct second‐order vertex‐based hierarchical honeycombs are constructed by iteratively replacing the vertices of a square‐based honeycomb with squares, circles, and octagons. Validated finite element models are then established to investigate the out‐of‐plane crashworthiness performance. Subsequently, the effect of the hierarchical geometry combinations and cell length ratios on the crashworthiness performance of the nine honeycombs is studied. The study showed that the second‐order hierarchical honeycomb exhibited superior crashworthiness performance under the same relative density compared to the regular and first‐order hierarchical square honeycombs. The study determined that the circle is a suitable matching geometry in the first‐ and second‐order hierarchies for improving the crashworthiness of a square‐based honeycomb. Using Complex Proportional Assessment, the Square‐Circle‐Circle ranked as the optimum structure for crashworthiness application. [ABSTRACT FROM AUTHOR]

In this paper, assuming the lightweight design is the main requirement, an efficient design of honeycomb sandwich tubes and its quasi-static compressive properties improvement were presented. The structures are designed in SolidWorks software, consisting of two face sheets and a honeycomb core implemented in its in-plane position. The axial compression tests are performed using Abaqus software. Detailed deformation features and energy absorption characteristics during the crushing process were presented. The compressive properties of the improved structures were determined from the energy absorption efficiency curves. Additionally, mathematical formulas for predicting the quasi-static compressive properties are presented. Theoretical predictions and FEA findings were in good agreement. In comparison to the standard structure, the suggested method greatly increased the structure's strength without adding mass to the design. [ABSTRACT FROM AUTHOR]

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This study examines a hierarchical vertex-based structure that improves the crashworthiness of the conventional multi-cell square, a biological hierarchy of natural origin with exceptional mechanical properties. The vertex-based hierarchical square structure (VHS) is explored for its geometric properties, including infinite repetition and self-similarity. The cut-and-patch method is used to derive an equation for the material thicknesses of different orders of the VHS based on the principle of the same weight. A thorough parametric study of VHS was conducted using LS-DYNA, which examined the effects of material thickness, orders, and various structural ratios. The results were evaluated based on common crashworthiness criteria and demonstrated that the total energy absorption (TEA), specific energy absorption (SEA), and mean crushing force ( P m ) of VHS exhibited similar monotonicity concerning the orders. SEA of the first-order VHS with λ 1 = 0.3 and the second-order VHS with λ 1 = 0.3 and λ 2 = 0.1 are improved by at most 59.9% and 102.4% respectively; the second-order VHS with 0.2 ≤ λ 1 ≤ 0.4 and 0.1 ≤ λ 2 ≤ 0.15 have the better overall performance of crashworthiness. Then, the half-wavelength equation of VHS and P m of each fold was established based on the Super-Folding Element method. Meanwhile, a comparative analysis with the simulation results reveals three different out-of-plane deformation mechanisms of VHS. The study indicated that material thickness had a greater impact on crashworthiness. Finally, the comparison with conventional honeycombs demonstrated that VHS holds great promise as a structure for crashworthiness. These results provide a solid foundation for further research and development of new bionic energy-absorbing devices. [ABSTRACT FROM AUTHOR]

The innovative design of microstructure topology is of great significance to improve the energy absorption performance of honeycombs. In this paper, by embedding a hexagonal substructure in each inclined wall of the traditional reentrant (RE) honeycomb, a novel auxetic honeycomb, called reentrant combined-wall (RCW) honeycomb, is developed for improving energy absorption. Combining the experimental methods, numerical simulations, and analytical analyses, we systematically studied the in-plane quasi-static behaviors of the proposed honeycomb structure. It can be found that the deformation of the RCW honeycomb has a transitional stage, which makes a significant stress enhancement. During the crushing process, the Poisson's ratio of the RCW honeycomb keeps negative and is lower than that of the RE honeycomb. Besides, numerical and analytical analyses show that the stress-strain response of the RCW honeycomb has a good designability. Further, the analysis of specific energy absorption (SEA) is also performed, in which the RCW honeycomb shows a significant superiority over the RE honeycomb, with the SEA value almost twice that of the latter. Therefore, it can be concluded that the proposed novel structure has tangible improvements in the crushing strength, auxetic performance, and energy absorption, which deserves more attention in future work. [ABSTRACT FROM AUTHOR]

This study investigated the capability of honeycomb core structures made of kenaf fibre-reinforced polylactic acid (PLA) composite. Two types of kenaf fibre were used in this study, these being woven kenaf and non-woven cotton/kenaf. Initially, the corrugated shape panel was manufactured using a hot moulding compression method. The panel was then cut into corrugated strips, bonded together using epoxy resin to form the honeycomb core structure, and balsa wood used as their skins. The effects of core height and crosshead displacement rate were investigated. The honeycomb core consisted of 20 mm, 30 mm and 40 mm core heights, and the crosshead displacement rate ranged from 2 mm/min to 500 min/min. Of all the samples, core structure with a height of 20 mm tested at 500 mm/min offered the highest value of compressive strength and specific energy absorption, which were 6.23 MPa and 12.36 kJ/kg, respectively. It was also discovered that the core height and loading rate have significant effects on the mechanical properties of the kenaf/PLA honeycomb core structure. [ABSTRACT FROM AUTHOR]

Aerogels, shaped as fibers, films, as well as monoliths, have demonstrated a plethora of applications in both academia and industry due to charming properties including ultralow density, large specific surface area, high porosity, etc., however studies on more complicated aerogel forms (e.g., honeycombs) with more powerful applications have not been fully explored. Herein, the Kevlar aerogel honeycomb is firstly constructed through a dry ice‐assisted 3D printing method, where the Kevlar nanofiber ink is printed directly in dry ice freezing atmosphere, followed by supercritical fluid drying. The subsequent 3D Kevlar/shear‐stiffening gel (SSG) honeycomb (3D‐KSH) can be obtained by selective nanoconfining of SSG into nanopores of the aerogel skeleton wall (with the loading amount of 93 wt%) rather than into open honeycomb channels, solving the leakage, creep deformation, and shape design infeasibility of the SSG. Combining the advantages of Kevlar, honeycomb and SSG, the fabricated 3D‐KSH shows obvious smart responsive behavior to external stimulus. Additionally, the 3D‐KSH has high strain rate sensitivity (sensitivity factor of 4.16 × 10−4) and excellent impact protection performance (energy absorption value up to 176 J g−1 at the strain rate of 6300 s−1), which will significantly broaden application prospect in some intelligent protection fields. [ABSTRACT FROM AUTHOR]

In order to pursue good crushing load uniformity and enchance energy absorption efficiency of conventional honeycombs, a kind of bio-inspired hierarchical honeycomb model is proposed by mimicking the arched crab shell structures. Three bio-inspired hierarchical honeycombs (BHHs) with different topologies are designed by replacing each vertex of square honeycombs with smaller arc-shaped structures. The effects of hierarchical topologies and multi-material layout on in-plane dynamic crushings and absorbed-energy capacities of the BHHs are explored based on the explicit finite element (FE) analysis. Different deformation modes can be observed from the BHHs, which mainly depend upon hierarchical topologies and impact velocities. According to energy efficiency method and one-dimensional (1D) shock theory, calculation formulas of densification strains and plateau stresses for the BHHs are derived to characterize the dynamic bearing capacity, which is consistent well with FE results. Compared with conventional honeycombs, the crushing load efficiency and energy absorption capacity of the BHHs can be improved by changing the proper hierarchical topology and multi-material layout. These researches will provide theoretical guidance for innovative design and dynamic response performance controllability of honeycombs. [ABSTRACT FROM AUTHOR]

The low-velocity impact response of aluminum honeycomb sandwich panels with composite face sheets is investigated using an LS-DYNA-based finite-element simulation. The finite-element model incorporates the damage, delamination, and failure capabilities, and a verification analysis of the results found. Suitable prediction models for the specific energy absorption and peak load at different values of geometrical parameters of the panels are developed using the response surface methodology. The effects of face sheet thickness, cell size, cell height, and cell thickness on the specific energy absorption and peak load are investigated. A multi-objective optimization of the panels is carried out for the maximum specific energy absorption and the minimum peak load. [ABSTRACT FROM AUTHOR]

Lightweight sandwich structures have been receiving significant attention. By studying and imitating the structure of biomaterials, its application in the design of sandwich structures has also been found to be feasible. With inspiration from the arrangement of fish scales, a 3D re-entrant honeycomb was designed. In addition, a honeycomb stacking method is proposed. The resultant novel re-entrant honeycomb was utilized as the core of the sandwich structure in order to increase the impact resistance of the sandwich structure under impact loads. The honeycomb core is created using 3D printing. By using low-velocity impact experiments, the mechanical properties of the sandwich structure with Carbon-Fiber-Reinforced Polymer (CFRP) face sheets under different impact energies were studied. To further investigate the effect of the structural parameters on the structural, mechanical properties, a simulation model was developed. Simulation methods examined the effect of structural variables on peak contact force, contact time, and energy absorption. Compared to traditional re-entrant honeycomb, the impact resistance of the improved structure is more significant. Under the same impact energy, the upper face sheet of the re-entrant honeycomb sandwich structure sustains less damage and deformation. The improved structure reduces the upper face sheet damage depth by an average of 12% compared to the traditional structure. In addition, increasing the thickness of the face sheet will enhance the impact resistance of the sandwich panel, but an excessively thick face sheet may decrease the structure's energy absorption properties. Increasing the concave angle can effectively increase the energy absorption properties of the sandwich structure while preserving its original impact resistance. The research results show the advantages of the re-entrant honeycomb sandwich structure, which has certain significance for the study of the sandwich structure. [ABSTRACT FROM AUTHOR]

This research aims to obtain the optimal honeycomb hybrid crash box design. Finite elements, parametric studies, and multi-objective optimization are carried out sequentially. Parametric studies are carried out to obtain important parameters to increase energy absorption and minimize mass. The effect of structure angle, honeycomb side length, and structure thickness are selected as the design parameter. Energy absorption and crash box mass are observed as design responses. Based on the results, it can be determined the optimal design from multi-objective optimization is angle structure of 21.1310, side length of 8.006 mm, and thickness of 1.2 mm. The model validation results for the optimal solution are appropriate; it is characterized by a honeycomb-filled structure that supports the folding of the outer wall of the crash box. [ABSTRACT FROM AUTHOR]

Honeycomb cores are widely used in the aerospace and automotive fields as a part of protective structures. Unfortunately, standard prismatic honeycomb cores offer a limited amount of energy absorption under lateral loads and suffer from degradation of their impact-deadening properties when their dimensional scale is increased. In this work, a multiscale study on energy absorption under quasi-static load is carried out on 3D-printed honeycomb core samples constituted by a variable section and compared to the cases of standard hexagonal honeycomb samples having the same mass and external dimensions. When doubling the dimensional scale in the case of lateral loads, the novel core geometry showed a substantial absence of specific energy absorption degradation, whereas the hexagonal core suffered from a 12.2%-degradation. Furthermore, by increasing the dimensional scale, the novel core geometry shows a delay in the densification onset. The variable-core geometry showed an average increase, in terms of energy absorption under lateral loads, of 46.8% for the regular scale and 71.4% for the double scale. Under axial loads, a 12.4%-decrease in energy absorption was observed for the samples with novel geometry, which, nevertheless, showed a relatively constant profile of reaction force under compression: this property could potentially allow it to avoid pre-crushing. [ABSTRACT FROM AUTHOR]